Java Question Handle return value with RaisEvent

XverhelstX · Jul 12, 2013

Hi

How is it possible to return an event from a raisevent from an external activity.

For example in Basic4Android we have this:

B4X:

Sub Activity_KeyPress (KeyCode As Int) As Boolean 'Return True to consume the event
   If Keycode = KeyCodes.KEYCODE_BACK Then
      Return False
   Else
      Return False
   End If   
End Sub

In java:

B4X:

@Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
      return false;
      
   }

How is it possible to let the user choose to return false or true when an event is raised to a b4a sub

Regards,
Tomas

Informatix · Jul 12, 2013

XverhelstX said:
How is it possible to let the user choose to return false or true when an event is raised to a b4a sub

raiseEvent and raiseEvent2 return an object by default. If you want to return a boolean, you just have to typecast the returned object.
Example:

B4X:

boolean YesNo = (boolean) m_Grid.m_BA.raiseEvent2(this, false, m_Grid.m_EventPrefix + "_question", true, new Object[] { this.X, this.Y });

XverhelstX · Jul 12, 2013

Informatix said:
raiseEvent and raiseEvent2 return an object by default. If you want to return a boolean, you just have to typecast the returned object.
Example:

B4X:

boolean YesNo = (boolean) m_Grid.m_BA.raiseEvent2(this, false, m_Grid.m_EventPrefix + "_question", true, new Object[] { this.X, this.Y });

Great and thanks!

daemon · Oct 30, 2014

What will happen if the event handler sub does not exist?

Informatix · Oct 30, 2014

daemon said:
What will happen if the event handler sub does not exist?

With RaiseEvent, nothing happens. With RaiseEvent2, it depends on the value of the second parameter.

Erel · Oct 30, 2014

Small comment about the original question.

This code is safer:

B4X:

Boolean yesNoOrNull = (Boolean)ba.raiseEvent(...);
boolean yesNo = yesNoOrNull != null && yesNoOrNull == true;

There are cases where raiseEvent or raiseEvent2 will return null. For example if the activity is currently not active.

Java Question Handle return value with RaisEvent

XverhelstX

Well-Known Member

Informatix

Expert

XverhelstX

Well-Known Member

daemon

Active Member

Informatix

Expert

Erel

B4X founder

Similar Threads

Java Question Handle return value with RaisEvent

XverhelstX

Well-Known Member

Informatix

Expert

XverhelstX

Well-Known Member

daemon

Active Member

Informatix

Expert

Erel

B4X founder

Similar Threads

Privacy & Transparency

Privacy & Transparency